An antenna impedance matching circuit designed for matching an antenna and a power amplifier impedance matching circuit designed for matching a power amplifier are necessary components of receiving/transmitting circuit of wireless communication systems. Modifying the power amplifier impedance matching circuit is a more complicated way of improving overall impedance matching. Therefore, instead, it is typical to modify the antenna impedance matching circuit to meet the requirement.
However, modifying the antenna impedance matching circuit needs lots of time for testing and simulating. It would delay the design schedule or result in cost increase under some conditions. For example, it is costly and time-consuming for a wireless circuit to obtain certification from a certification institute. Therefore once the antenna circuit including the antenna and the antenna impedance matching circuit is certified, keeping it unchanged would be a designer's first choice. Therefore the power amplifier impedance matching circuit would be modified instead. The most common method of modifying the impedance matching circuit is a “trial and error” one, which costs much effort. Hence another method for designing the impedance matching circuit to make the phase error meet the specification without altering an already certified circuit is needed.